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Chap. Two: Chemical Interactions Atoms and the Periodic Table STRUCTURE and Parts of ATOMS 118 “basic kinds” of matter Elements 92 naturally occurring (26 created in LABS) All listed on periodic table of elements Building blocks of everything on Earth Atoms – smallest unit (pieces) of elements – Atoms combine to form compounds STRUCTURE OF AN ATOM Protons • in the nucleus – center of the atom • positively charged • mass of “1” (AMU) EQUALS ATOMIC NUMBER ATOMIC STRUCTURE…(cont’d) Neutrons – have no electrical charge – mass of “1” (AMU) • AMU = “atomic mass unit” – in the nucleus – number may vary ATOMIC STRUCTURE (cont’d) Electrons – negatively charged – mass of “0” – in energy shells, or “orbits” surrounding the nucleus ELECTRON DISTRIBUTION Electrons are organized in “clouds” or energy levels. 4 shells • • • • 2 in the first 8 in the second 8 in the third 2 in the last Generally 8 is the most stable configuration. Electrons and Chemical Bonding “Sharing is caring…unless you’re ionic and then you just steal.” What do electrons do? Attractions between electrons in their shells causes chemical bonds to form. Chemical bonds occur so that each atom in the molecule has 8 in its outermost shell. There are TWO types of chemical bonds: Ionic and Covalent ELECTRON DISTRIBUTION…cont’d All atoms “want” 8 electrons in their outermost shells and will interact with other atoms to the end that all reach 8. TYPES OF CHEMICAL BONDS IONIC - one atom loses electrons, other gains electrons. – atoms that lose electrons become more positively charged – atoms that gain electrons become more negatively charged This process forms IONS!! TYPES OF CHEMICAL BONDS…cont’d COVALENT two atoms share one or more pairs of electrons. Each has 8 electrons in its outermost orbit.